A new rhodamine-thiourea/Al3+ complex sensor for the fast visual detection of arginine in aqueous media

A new naked-eye fluorescent sensor composed of bis-rhodamine-thiourea/Al3+ complex has been developed targeting the detection of arginine. It displayed high sensitivity and selectivity toward arginine over other analytes in aqueous media. In the presence of arginine, the complex sensor can give dual responsive signals of a visible color change and an ‘on–off’ fluorescence change within 1 min due to the opening-closure transformation of the spiro ring in rhodamine. More importantly, the complex sensor has a widely linear detection range of 0–1.2 × 10−4 mol L−1 toward arginine under the experimental conditions, which exceeded the concentration range in healthy body plasma samples. It demonstrates the potential application in plasma samples for real-time analysis.